The invention relates to a line protection switch for protecting an electrical load circuit from an over-current which exceeds a permissible load current.
Such line protection switches are known from the prior art. An example of such a line protection switch is, for example, a relay in which a coil through which load current flows in the event of over-current attracts an armature which is connected to a switching member. As long as the load current is in the permissible range, a spring acts counter to the magnetic attraction force of the coil. As the load current increases, the force produced by the coil also increases. As soon as the load current reaches an over-current value, the counter-force of the coil exceeds the retention force of the spring and the switching circuit is interrupted by means of mechanical actuation of a switching member which is connected to the armature. In order to prevent renewed closure of the switching circuit owing to the over-current which is no longer present, mechanical or magnetic catch mechanisms are often provided. These not only increase the number of necessary components in the switch and consequently the weight and volume thereof, but also constitute additional potential sources of error. Furthermore, it is necessary with magnetic catch mechanisms to guide the load current path inside the switching device once more.
A further disadvantage of this type of line protection switch is that, owing to the increasing forces, the components must be constructed in a correspondingly stable and solid manner. This not only increases the weight and the size of the line protection switch as a whole, but also allows the line protection switch to become more inert owing to the masses to be moved.